Biomarkers are essential tools in clinical research and practice. Useful biomarkers must combine good measurability, validated association with biological processes or outcomes, and should support clinical decision making if used in clinical practice. Several types of validated biomarkers have been reported in the context of bone diseases. However, because these biomarkers face certain limitations there is an interest in the identification of novel biomarkers for bone diseases, specifically in those that are tightly linked to the disease pathology leading to increased fracture-risk. MicroRNAs (miRNAs) are the most abundant RNA species to be found in cell-free blood. Encapsulated within microvesicles or bound to proteins, circulating miRNAs are remarkably stable analytes that can be measured using gold-standard technologies such as quantitative polymerase-chain-reaction (qPCR). Nevertheless, the analysis of circulating miRNAs faces several pre-analytical as well as analytical challenges. From a biological view, there is accumulating evidence that miRNAs play essential roles in the regulation of various biological processes including bone homeostasis. Moreover, specific changes in miRNA transcription levels or miRNA secretory levels have been linked to the development and progression of certain bone diseases. Only recently, results from circulating miRNAs analysis in patients with osteopenia, osteoporosis and fragility fractures have been reported. By comparing these findings to studies on circulating miRNAs in cellular senescence and aging or muscle physiology and sarcopenia, several overlaps were observed. This suggests that signatures observed during osteoporosis might not be specific to the pathophysiology in bone, but rather integrate information from several tissue types. Despite these promising first data, more work remains to be done until circulating miRNAs can serve as established and robust diagnostic tools for bone diseases in clinical research, clinical routine and in personalized medicine.

Objective To evaluate whether T2 relaxation time measurements obtained at 3 Tesla Magnetic Resonance Imaging (MRI) predict the onset of radiographic knee osteoarthritis (OA). Methods and Materials We performed a nested case-control study of incident radiographic knee OA in the Osteoarthritis Initiative (OAI) cohort. Cases were 50 knees with baseline KL grade of 0 that developed KL grade of 2 or more over a 4-year period. Controls were 80 knees with KL grade of 0 after four years of follow-up. Baseline T2 relaxation time measurements and laminar analysis of T2 in deep and superficial layers were performed in all knee compartments. The association of T2 values with incident OA was assessed with logistic regression and differences in T2 values by case-control status with linear regression, adjusting for age, sex, body mass index (BMI) and other covariates. Results Baseline T2 values in all compartments except the medial tibia were significantly higher in knees that developed OA compared to controls, and were particularly elevated in the superficial cartilage layers in all compartments. There was an increased likelihood of incident knee OA associated with higher baseline T2 values particularly in the patella, adjusted odds ratio (OR) per 1 SD increase in T2: 3.37 (95% CI: 1.72; 6.62), but also in the medial femur: 1.90 (1.07; 3.39), lateral femur: 2.17 (1.11; 4.25) and lateral tibia: 2.23 (1.16; 4.31). Conclusions These findings suggest that T2 values assessed when radiographic changes are not yet apparent may be useful in predicting the development of radiological tibiofemoral OA.

Standard DXA measurements, including Fracture Risk Assessment Tool (FRAX) scores, have shown limitations in assessing fracture risk in Type 2 Diabetes (T2D), underscoring the need for novel biomarkers and suggesting that other pathomechanisms may drive diabetic bone fragility. MicroRNAs (miRNAs) are secreted into the circulation from cells of various tissues proportional to local disease severity and were recently found to be crucial to bone homeostasis and T2D. Here, we studied, if and which circulating miRNAs or combinations of miRNAs can discriminate best fracture status in a well-characterized study of diabetic bone disease and postmenopausal osteoporosis (n ¼ 80 postmenopausal women). We then tested the most discriminative and most frequent miRNAs in vitro. Using miRNA-qPCR-arrays, we showed that 48 miRNAs can differentiate fracture status in T2D women and that several combinations of four miRNAs can discriminate diabetes-related fractures with high specificity and sensitivity (area under the receiver-operating characteristic curve values [AUCs], 0.92 to 0.96; 95% CI, 0.88 to 0.98). For the osteoporotic study arm, 23 miRNAs were fracture-indicative and potential combinations of four miRNAs showed AUCs from 0.97 to 1.00 (95% CI, 0.93 to 1.00). Because a role in bone homeostasis for those miRNAs that were most discriminative and most present among all miRNA combinations had not been described, we performed in vitro functional studies in human adipose tissue-derived mesenchymal stem cells to investigate the effect of miR-550a-5p, miR-188-3p, and miR-382-3p on osteogenesis, adipogenesis, and cell proliferation. We found that miR-382-3p significantly enhanced osteogenic differentiation (p < 0.001), whereas miR-550a-5p inhibited this process (p < 0.001). Both miRNAs, miR-382-3p and miR-550a-5p, impaired adipogenic differentiation, whereas miR-188-3p did not exert an effect on adipogenesis. None of the miRNAs affected significantly cell proliferation. Our data suggest for the first time that miRNAs are linked to fragility fractures in T2D postmenopausal women and should be further investigated for their diagnostic potential and their detailed function in diabetic bone.

OBJECTIVE To investigate compositional cartilage changes measured with 3T MRI-based T2 values over 48 months in overweight and obese individuals with different degrees of weight loss and to study whether weight loss slows knee cartilage degeneration and symptom worsening. DESIGN We studied participants from the Osteoarthritis Initiative with risk factors or radiographic evidence of mild to moderate knee OA with a baseline BMI ≥25kg/m2. We selected subjects who over 48 months lost a, moderate (BMI change, 5-10%, n=180) or large amount of weight (≥10%, n=78) and frequency-matched these to individuals with stable weight relative to their baseline BMI (<3%, n=258). T2 maps of the cartilage compartments of the right knee, grey-level co-occurrence matrix (GLCM) texture and laminar analyses were evaluated and associations with weight loss and clinical symptoms (WOMAC subscales for pain, stiffness and disability) were assessed using multivariable regression models adjusting for age, sex, baseline BMI and KL. RESULTS The amount of weight change was significantly associated with change in cartilage T2 of the medial tibia (β 0.9ms, 95%CI 0.4 to 1.1, P=0.001). An increase of T2 in the medial tibia was significantly associated with an increase in WOMAC pain (β 0.5ms, 95%CI 0.2 to 0.6, P=0.02) and disability (β 0.03ms, 95%CI 0.003 to 0.05, P=0.03. GLCM contrast and variance over all compartments showed significantly less progression in the >10% weight loss group compared to the stable weight group (both comparisons, P=0.04). CONCLUSIONS Weight loss over 48 months is associated with slowed knee cartilage degeneration and improved knee symptoms.

Summary While type 2 diabetes (T2D) is associated with higher skeletal fragility, specific risk stratification remains incompletely understood. We found volumetric bone mineral density, geometry, and serum sclerostin differences between low-fracture risk and high-fracture risk T2D women. These features might help identify T2D individuals at high fracture risk in the future. Introduction Diabetic bone disease, an increasingly recognized complication of type 2 diabetes mellitus (T2D), is associated with high skeletal fragility. Exactly which T2D individuals are at higher risk for fracture, however, remains incompletely understood. Here, we analyzed volumetric bone mineral density (vBMD), geometry, and serum sclerostin levels in two specific T2D subsets with different fracture risk profiles. We examined a T2D group with prior history of fragility fractures (DMFx, assigned high-risk group) and a fracture-free T2D group (DM, assigned low-risk group) and compared their results to nondiabetic controls with (Fx) and without fragility fractures (Co). Methods Eighty postmenopausal women (n=20 per group) underwent quantitative computed tomography (QCT) to compute vBMD and bone geometry of the proximal femur. Additionally, serum sclerostin, vitamin D, parathyroid hormone (PTH), HbA1c, and glomerular filtration rate (GFR) levels were measured. Statistical analyses employed linear regression models. Results DMFx subjects exhibited up to 33 % lower femoral neck vBMD than DM subjects across all femoral sites (−19 %≤ΔvBMD≤−33 %, 0.008≤p≤0.021). Additionally, DMFx subjects showed significantly thinner cortices (−6 %, p=0.046) and a trend toward larger bone volume (+10 %, p= 0.055) relative to DM women and higher serum sclerostin levels when compared to DM (+31.4 %, p=0.013), Fx (+ 25.2 %, p=0.033), and control (+22.4 %, p=0.028) subjects. Conclusion Our data suggest that volumetric bone parameters by QCT and serum sclerostin levels can identify T2D individuals at high risk of fracture and might therefore show promise as clinical tools for fracture risk assessment in T2D. However, future research is needed to establish diabetes-specific QCTand sclerostin-reference databases.